The aim of the proposed research is to use a genomic approach to generate a deeper understanding of the biology of winged morph induction and development in an emerging genomic model system, the pea aphid (Acyrthosiphon pisum). In this species, normally wingless asexually reproducing females produce winged offspring in response to environmental stimuli such as overcrowding or poor host plant quality. In contrast, males are winged or unwinged depending on the allele they carry of a gene on the X chromosome. The specific aims are to use pea aphid cDNA microarrays to i) examine the changes in gene expression that result from exposure of aphid mothers to wing-inducing cues and ii) examine changes in gene expression that accompany the development of the winged and unwinged morphs of both females and males. These experiments will generate hypotheses about which genetic pathways are involved in the i) induction and ii) development and maintentance of winged and unwinged morphs. These hypotheses will then be tested by examination of candidate genes using traditional approaches. Overall, experiments in the proposed research will provide insight into the developmental genetic basis of extreme phenotypic plasticity. [unreadable] [unreadable] [unreadable]